Quantitative analysis of regulatory T cells in kidney graft recipients: a relationship with calcineurin inhibitor level

Cyclosporine A induces hepatotoxicity in zebrafish larvae via upregulating oxidative stress

As a powerful immunosuppressant, cyclosporine A (CsA) is widely used clinically. However, it has been found to have many side effects including nephrotoxicity and neurotoxicity. Despite this, some patients cannot avoid using CsA during pregnancy and this can be detrimental to both the patient and the foetus. This study used zebrafish as a model animal to evaluate the hepatotoxic effects of CsA in zebrafish embryos. Zebrafish embryos cultured at 72 post-fertilization (hpf) were exposed to three concentrations of CsA at 2.5 mg/L, 5 mg/L, and 10 mg/L for 72 h. Liver developmental defects, smaller or missing swim bladder, slower heart rate, reduced body length, and delayed yolk sac absorption were observed. The level of oxidative stress (ROS) increased with the increase of CsA concentration. The indicators of related oxidative stress kinase activities including malondialdehyde (MDA), catalase (CAT) and SOD, all appeared to significantly increased. The use of astaxanthin (ATX) to inhibit oxidative stress was found to be useful for rescuing zebrafish hepatic development defects. Therefore, our results suggest that CsA induces zebrafish embryonic hepatic development defects by activating the oxidative stress. The study of CsA-induced hepatic development defects of zebrafish embryos is helpful for clinical evaluation of the safety of CsA and enables the search for new use without side effects.

Expansion and characterization of regulatory T cell populations from Korean kidney transplant recipients

The development of immunosuppressants has enabled remarkable progress in kidney transplantation (KT). However, current immunosuppressants cannot induce immune tolerance, and their nonspecific immunosuppressive effects result in many adverse effects. Regulatory T cells (Tregs) play crucial roles in controlling all specific immune responses. This study evaluated the distribution of Tregs and their effects on kidney allograft function in Korean KT recipients. We enrolled 113 KT recipients with stable graft function. The differentiation and expansion of Tregs were examined by flow cytometry to compare the Tregs subpopulations. Among the 113 patients, 73 (64.6%) were males, and the mean follow-up period from KT to Tregs collection was 147.5 + 111.3 months. Patients receiving lower doses of cyclosporine had higher proportions of Tregs than those with higher doses of cyclosporine (36.3 + 21.6 vs 17.0 + 12.7, P = .010, respectively). Patients taking cyclosporine tended to have higher Tregs numbers than those taking tacrolimus (94.7 + 158.1 vs 49.3 + 69.4, P = .095, respectively). However, no significant association was observed between Tregs and allograft dysfunction in the cox proportional hazard model. Tregs counts may be associated with the type and dose of immunosuppressants. However, no significant relationship was found between Tregs and kidney allograft function in stable KT recipients.

Regulatory T Cells for the Induction of Transplantation Tolerance

Organ transplantation is the optimal treatment for terminal and irreversible organ failure. Achieving transplantation tolerance has long been the ultimate goal in the field of transplantation. Regulatory T cell (Treg)-based therapy is a promising novel approach for inducing donor organ-specific tolerance. Tregs play critical roles in the maintenance of immune homeostasis and self-tolerance, by promoting transplantation tolerance through a variety of mechanisms on different target cells, including anti-inflammatory cytokine production, induction of apoptosis, disruption of metabolic pathways, and mutual interaction with dendritic cells. The continued success of Treg-based therapy in the clinical setting is critically dependent on preclinical studies that support its translational potential. However, although some initial clinical trials of adoptive Treg therapy have successively demonstrated safety and efficacy for immunosuppressant minimization and transplantation tolerance induction, most Treg-based hematopoietic stem cell and solid organ clinical trials are still in their infancy. These clinical trials have not only focused on safety and efficacy but also included optimization and standardization protocols of good manufacturing practice regarding cell isolation, expansion, dosing, timing, specificity, quality control, concomitant immunosuppressants, and post-administration monitoring. We herein report a brief introduction of Tregs, including their phenotypic and functional characterization, and focus on the clinical translation of Treg-based therapeutic applications in the setting of transplantation.

Combined low-dose everolimus and low-dose tacrolimus after Alemtuzumab induction therapy: a randomized prospective trial in lung transplantation

Background

Long-term outcomes of lung transplantation are severely affected by comorbidities and development of chronic rejection. Among the comorbidities, kidney insufficiency is one of the most frequent and it is mainly caused by the cumulative effect of calcineurin inhibitors (CNIs). Currently, the most used immunosuppression protocols worldwide include induction therapy and a triple-drug maintenance immunosuppression, with one calcineurin inhibitor, one anti-proliferative drug, and steroids. Our center has pioneered the use of alemtuzumab as induction therapy, showing promising results in terms of short- and long-term outcomes. The use of alemtuzumab followed by a low-dose double drug maintenance immunosuppression, in fact, led to better kidney function along with excellent results in terms of acute rejection, chronic lung allograft dysfunction, and survival (Benazzo et al., PLoS One 14(1):e0210443, 2019). The hypothesis driving the proposed clinical trial is that de novo introduction of low-dose everolimus early after transplantation could further improve kidney function via a further reduction of tacrolimus. Based on evidences from kidney transplantation, moreover, alemtuzumab induction therapy followed by a low-dose everolimus and low-dose tacrolimus may have a permissive action on regulatory immune cells thus stimulating allograft acceptance.

Methods

A randomized prospective clinical trial has been set up to answer the research hypothesis. One hundred ten patients will be randomized in two groups. Treatment group will receive the new maintenance immunosuppression protocol based on low-dose tacrolimus and low-dose everolimus and the control group will receive our standard immunosuppression protocol. Both groups will receive alemtuzumab induction therapy. The primary endpoint of the study is to analyze the effect of the new low-dose immunosuppression protocol on kidney function in terms of eGFR change. The study will have a duration of 24 months from the time of randomization. Immunomodulatory status of the patients will be assessed with flow cytometry and gene expression analysis.

Discussion

For the first time in the field of lung transplantation, this trial proposes the combined use of significantly reduced tacrolimus and everolimus after alemtuzumab induction. The new protocol may have a twofold advantage: (1) further reduction of nephrotoxic tacrolimus and (2) permissive influence on regulatory cells development with further reduction of rejection episodes.

Trial registration

EUDRACT Nr 2018-001680-24. Registered on 15 May 2018

Phenotype and molecular signature of CD8+ T cell subsets in T cell- mediated rejections after kidney transplantation

We investigated the phenotype and molecular signatures of CD8+ T cell subsets in kidney-transplant recipients (KTRs) with biopsy-proven T cell-mediated rejection (TCMR). We included 121 KTRs and divided them into three groups according to the pathologic or clinical diagnosis: Normal biopsy control (NC)(n = 32), TCMR (n = 50), and long-term graft survival (LTGS)(n = 39). We used flowcytometry and microarray to analyze the phenotype and molecular signatures of CD8+ T cell subsets using peripheral blood from those patients and analyzed significant gene expressions according to CD8+ T cell subsets. We investigated whether the analysis of CD8+ T cell subsets is useful for predicting the development of TCMR. CCR7+CD8+ T cells significantly decreased, but CD28nullCD57+CD8+ T cells and CCR7-CD45RA+CD8+ T cells showed an increase in the TCMR group compared to other groups (p<0.05 for each); hence CCR7+CD8+ T cells showed significant negative correlations to both effector CD8+ T cells. We identified genes significantly associated with the change of CCR7+CD8+ T, CCR7-CD45RA+CD8+ T, and CD28nullCD57+CD8+ T cells in an ex vivo study and found that most of them were included in the significant genes on in vitro CCR7+CD8+ T cells. Finally, the decrease of CCR7+CD8+ T cells relative to CD28nullCD57+ T or CCR7-CD45RA+CD8+ T cells can predict TCMR significantly in the whole clinical cohort. In conclusion, phenotype and molecular signature of CD8+ T subsets showed a significant relationship to the development of TCMR; hence monitoring of CD8+ T cell subsets may be a useful for predicting TCMR in KTRs.

The safety, immunological benefits, and efficacy of ginseng in organ transplantation

Korean ginseng (Panax ginseng) is associated with a variety of therapeutic effects, including antioxidative, anti-inflammatory, vasorelaxative, antiallergic, antidiabetic, and anticancer effects. Accordingly, the use of ginseng has reached an all-time high among members of the general public. However, the safety and efficacy of ginseng in transplant recipients receiving immunosuppressant drugs have still not been elucidated. Transplantation is the most challenging and complex of surgical procedures and may require causation for the use of ginseng. In this regard, we have previously examined the safety, immunological benefits, and protective mechanisms of ginseng with respect to calcineurin inhibitor-based immunosuppression, which is the most widely used regimen in organ transplantation. Using an experimental model of calcineurin inhibitor-induced organ injury, we found that ginseng does not affect drug levels in the peripheral blood and tissue, favorably regulates immune response, and protects against calcineurin inhibitor-induced nephrotoxicity and pancreatic islet injury. On the basis of our experimental studies and a review of the related literature, we propose that ginseng may provide benefits in organ transplant recipients administered calcineurin inhibitors. Through the present review, we aimed to briefly discuss our current understanding of the therapeutic benefits of ginseng related to transplant patient survival.

The Tumor Microenvironment in Post-Transplant Lymphoproliferative Disorders

Post-transplant lymphoproliferative disorders (PTLDs) cover a broad spectrum of lymphoproliferative lesions arising after solid organ or allogeneic hematopoietic stem cell transplantation. The composition and function of the tumor microenvironment (TME), consisting of all non-malignant constituents of a tumor, is greatly impacted in PTLD through a complex interplay between 4 factors: 1) the graft organ causes immune stimulation through chronic antigen presentation; 2) the therapy to prevent organ rejection interferes with the immune system; 3) the oncogenic Epstein-Barr virus (EBV), present in 80% of PTLDs, has a causative role in the oncogenic transformation of lymphocytes and influences immune responses; 4) interaction with the donor-derived immune cells accompanying the graft. These factors make PTLDs an interesting model to look at cancer-microenvironment interactions and current findings can be of interest for other malignancies including solid tumors. Here we will review the current knowledge of the TME composition in PTLD with a focus on the different factors involved in PTLD development.

Effects of resveratrol on Th17 cell-related immune responses under tacrolimus-based immunosuppression

BACKGROUND

We previously reported that tacrolimus (Tac) does not decrease T helper 17 cells (Th17) response in kidney transplantation. In this study, we evaluated whether Resveratrol (Resv) has immunosuppressive effects by decreasing Th17 responses in Tac-based immunosuppression.

METHODS

We investigated the effects of Resv under Tac-treatment conditions, on CD4+ T cell differentiation to Th17 cells in peripheral blood mononuclear cells (PBMCs), and proliferation of CD4+ T cells co-cultured with human renal proximal tubular epithelial cells (HRPTEpiCs). The effects of Resv on Th17 cells were tested in the murine skin transplant model.

RESULTS

In PBMCs, Tac did not but combination of Tac and Resv further suppressed Th17 immune response. In the co-culture study, combination of Resv to Tac significantly decreased HRPTEpiC-induced T cell proliferation compared to Tac alone. Resv treatment in the Jurkat cell induced the expression of AMP-activated protein kinase and suppressed the expression of mammalian target of rapamycin (mTOR), suggesting blocking Th17 pathway by Resv. In the murine skin transplant model, combination of Resv to Tac significantly prolonged skin graft survival accompanied by the suppression of Th17 cells, compared to either the Tac-alone or control groups.

CONCLUSION

The results of our study suggest that Resv provides additional immunosuppressive effects to Tac by suppressing effector CD4+ T cells, especially Th17 cells, in the transplantation setting.

Th1, Th2, Th17 cell subsets in two different immunosuppressive protocols in renal allograft recipients (Sirolimus vs mycophenolate mofetil): A cohort study

Long-term use of calcineurin inhibitors (CNI) is associated with nephrotoxicity, which is an important cause of renal dysfunction. Therefore, CNI-minimization strategies which decrease the CNI nephrotoxicity under the protection of additional immunosuppressant drugs have been developed. The aim of current cohort study was to compare the effect of two immunosuppressive protocols [tacrolimus (TAC) in combination with mycophenolate mofetil (MMF) and prednisolone (PRED) versus TAC in combination with sirolimus (SRL) and prednisolone] on the frequency of T helper cell subsets (Th1, Th2 and Th17 cells) and their associated cytokine (IFN-γ, IL-4 and IL-17A) levels in renal allograft recipients. In this study, renal transplant recipients who received induction therapy (Antithymocyte globulin) and were also on triple immunosuppressive therapy were included and divided in to two groups: Group A was comprised 14 patients who received TAC, MMF and PERD whereas group B was composed of 10 patients who received TAC, SRL and PERD. The frequency of Th1, Th2 and Th17 cells in the peripheral blood mononuclear cells (PBMCs) of the patients was analyzed by flow cytometry before and 4 months after transplantation. In addition, IFN-γ, IL-4 and IL-17A concentrations in PBMC culture supernatants of patients before and 4 months after transplantation were quantified by ELISA. The results of our study showed that TAC, MMF and PRED protocol did not diminish the frequency of Th17 cells at 4 months post-transplantation (5% ± 2.5) compared with pre-transplantation (2.3% ± 1; P < 0.05). However, Th17 (3.6% ± 1.5 pre-transplantation vs 2.2% ± 0.9 at 4 months post-transplantation; P < 0.05), Th2 (1.4% ± 0.3 pre-transplantation vs 0.8% ± 0.4 at 4 months post-transplantation; P < 0.05) cell subsets and IL-4 concentration (71.5 pg/ml ± 12 pre-transplantation vs 62.5 pg/ml ±4.4 at 4 months post-transplantation; P < 0.05) were significantly decreased after transplantation in patients who had received SRL, TAC and PRED. In conclusion, the data of the current study suggest that using reduced dose of TAC in SRL, TAC and PRED protocol is in favor of allograft survival; however a cohort study with larger sample size is needed for confirming our results.

Clinical significance of Th17 cells in kidney transplantation

Transplantation research has focused on cytotoxic T-cell and plasma cell/B-cell-targeted strategies, but little attention has been paid to the role of T helper 17 (Th17) cells in allograft dysfunction. However, accumulating evidence suggests that Th17 cells contribute to the development of acute and chronic allograft injury after transplantation of various organs, including the kidney. This review summarizes recent reports on the role of Th17 cells in kidney transplantation. Means of improving allograft outcomes by targeting the Th17 pathway are also suggested.

The Calcineurin Inhibitor Tacrolimus Specifically Suppresses Human T Follicular Helper Cells

Background

T follicular helper (Tfh) cells are key players in the production of antibody-producing B cells via the germinal center reaction. Therapeutic strategies targeting Tfh cells are important where antibody formation is implicated in disease, such as transplant rejection and autoimmune diseases. We investigated the impact of the immunosuppressive agent tacrolimus on human Tfh cell differentiation and function in transplant recipients.

Methods

Paired blood and lymph node (LN) samples were obtained from 61 transplant recipients immediately prior to organ implantation. Living-donor recipients received a week of tacrolimus prior to kidney transplantation. Deceased-donor recipients served as controls, as tacrolimus was not administered until after the transplant operation. Flow cytometry was used to compare LN and circulating cell subsets.

Results

The calcineurin inhibitor (CNIs) tacrolimus specifically suppresses both LN Tfh cells and circulating Tfh cells, but not their regulatory counterparts or other CD4 T cell subsets.

Conclusion

Our findings suggest that CNIs may have a more important role in the prevention of antibody formation than previously understood and, therefore, have potential for antibody-associated conditions in which aberrant Tfh function has been implicated in disease.

Suppressive Effect of 1α,25-Dihydroxyvitamin D3 on Th17-Immune Responses in Kidney Transplant Recipients With Tacrolimus-Based Immunosuppression

BACKGROUND

The aim of this study was to investigate whether 1α,25-dihydroxyvitamin D3 can regulate Th17-related immune responses in kidney transplant recipients (KTRs) being treated with tacrolimus (Tac)-based immunosuppression.

METHODS

First, we evaluated the effect of 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) on Th17-immune responses in an in vitro study using peripheral blood mononuclear cells (PBMCs) from healthy volunteers or KTRs. Next, we investigated mammalian target of rapamycin/STAT3 signaling as a mechanism by which 1,25(OH)2D3 exerted its effect on T cells using the Jurkat cell line. Third, we investigated Th17-cytokine levels or Th17 cell percentage in PBMCs according to the serum 25-hydroxyvitamin D (25(OH)D) level in 81 KTRs, and we performed a prospective study to assess whether 1,25(OH)2D3 (calcitriol) treatment decreased Th17 cytokine levels (IL-17, IL-22) in 42 KTRs.

RESULTS

In the in vitro study, we observed that the addition of 1,25(OH)2D3 to Tac significantly inhibited the appearance of IL-17-positive cells in culture. The expression of IL-17 and IL-22 messenger RNA in PBMCs was also decreased by the addition of 1,25(OH)2D3. In the Jurkat cell line, the mTOR/STAT3 pathway was further downregulated with the addition of 1,25(OH)2D3 to Tac. In the 81 KTRs, the 25(OH)D level was inversely correlated with the Th17 cytokine levels or the proportion of Th17 cell out of CD4 T cells. Treatment with calcitriol for 6 months significantly decreased Th17 cytokine levels compared with the baseline values in another 42 KTRs.

CONCLUSIONS

Treatment with 1,25(OH)2D3 may have immunologic benefits by effectively suppressing the Th17-related immune responses in KTRs on Tac-based immunosuppression.

Expanding Diversity and Common Goal of Regulatory T and B Cells. II: In Allergy, Malignancy, and Transplantation

Regulation of immune response was found to play an important role in the course of many diseases such as autoimmune diseases, allergy, malignancy, organ transplantation. The studies on immune regulation focus on the role of regulatory cells (Tregs, Bregs, regulatory myeloid cells) in these disorders. The number and function of Tregs may serve as a marker of disease activity. As in allergy, the depletion of Tregs is observed and the results of allergen-specific immunotherapy could be measured by an increase in the population of IL-10⁺ regulatory cells. On the basis of the knowledge of anti-cancer immune response regulation, new directions in therapy of tumors are introduced. As the proportion of regulatory cells is increased in the course of neoplasm, the therapeutic action is directed at their inhibition. The depletion of Tregs may be also achieved by an anti-check-point blockade, anti-CD25 agents, and inhibition of regulatory cell recruitment to the tumor site by affecting chemokine pathways. However, the possible favorable role of Tregs in cancer development is considered and the plasticity of immune regulation should be taken into account. The new promising direction of the treatment based on regulatory cells is the prevention of transplant rejection. A different way of production and implementation of classic Tregs as well as other cell types such as double-negative cells, Bregs, CD4⁺ Tr1 cells are tested in ongoing trials. On the basis of the results of current studies, we could show in this review the significance of therapies based on regulatory cells in different disorders.

Impact of Immune-Modulatory Drugs on Regulatory T Cell

Immunosuppression strategies that selectively inhibit effector T cells while preserving and even enhancing CD4FOXP3 regulatory T cells (Treg) permit immune self-regulation and may allow minimization of immunosuppression and associated toxicities. Many immunosuppressive drugs were developed before the identity and function of Treg were appreciated. A good understanding of the interactions between Treg and immunosuppressive agents will be valuable to the effective design of more tolerable immunosuppression regimens. This review will discuss preclinical and clinical evidence regarding the influence of current and emerging immunosuppressive drugs on Treg homeostasis, stability, and function as a guideline for the selection and development of Treg-friendly immunosuppressive regimens.

Combining Exosomes Derived from Immature DCs with Donor Antigen-Specific Treg Cells Induces Tolerance in a Rat Liver Allograft Model

Allograft tolerance is the ultimate goal in the field of transplantation immunology. Immature dendritic cells (imDCs) play an important role in establishing tolerance but have limitations, including potential for maturation, short lifespan in vivo and short storage times in vitro. However, exosomes (generally 30–100 nm) from imDCs (imDex) retain many source cell properties and may overcome these limitations. In previous reports, imDex prolonged the survival time of heart or intestine allografts. However, tolerance or long-term survival was not achieved unless immune suppressants were used. Regulatory T cells (Tregs) can protect allografts from immune rejection, and our previous study showed that the effects of imDex were significantly associated with Tregs. Therefore, we incorporated Tregs into the treatment protocol to further reduce or avoid suppressant use. We defined the optimal exosome dose as approximately 20 μg (per treatment before, during and after transplantation) in rat liver transplantation and the antigen-specific role of Tregs in protecting liver allografts. In the co-treatment group, recipients achieved long-term survival, and tolerance was induced. Moreover, imDex amplified Tregs, which required recipient DCs and were enhanced by IL-2. Fortunately, the expanded Tregs retained their regulatory ability and donor-specificity. Thus, imDex and donor-specific Tregs can collaboratively induce graft tolerance.

Pharmacologic targeting of regulatory T cells for solid organ transplantation: current and future prospects

The last three decades have witnessed significant advances in the development of immunosuppressive medications used in kidney transplantation leading to a remarkable gain in short-term graft function and outcomes. Despite these major breakthroughs, improvements in long-term outcomes lag behind due to a stalemate between drug-related nephrotoxicity and chronic rejection typically due to donor-specific antibodies. Regulatory T cells (Tregs) have been shown to modulate the alloimmune response and can exert suppressive activity preventing allograft rejection in kidney transplantation. Currently available immunosuppressive agents impact Tregs in the alloimmune milieu with some of these interactions being deleterious to the allograft while others may be beneficial. Variable effects are seen with common antibody induction agents such that basiliximab, an IL-2 receptor blocker, decreases Tregs while lymphocyte depleting agents such as antithymocyte globulin increase Tregs. Calcineurin inhibitors, a mainstay of maintenance immunosuppression since the mid-1980s, seem to suppress Tregs while mammalian targets of rapamycin (less commonly used in maintenance regimens) expand Tregs. The purpose of this review is to provide an overview of Treg biology in transplantation, identify in more detail the interactions between commonly used immunosuppressive agents and Tregs in kidney transplantation and lastly describe future directions in the use of Tregs themselves as therapy for tolerance induction.

The effect of mammalian target of rapamycin inhibition on T helper type 17 and regulatory T cell differentiation in vitro and in vivo in kidney transplant recipients

Sirolimus (SRL) is a promising alternative to calcineurin inhibitors, such as tacrolimus (TAC), in kidney transplant recipients (KTRs), but the immunological benefits of conversion from calcineurin inhibitors to SRL are not fully investigated. In the present study, we evaluated the effect of conversion from TAC to SRL on the T helper type 17/regulatory T (Th17/Treg) axis in three separate studies. First, the effect of SRL on the Th17/Treg axis was evaluated in vitro using peripheral blood mononuclear cells (PBMCs). Second, the effect of conversion from TAC to SRL on the Th17/Treg axis was studied in KTRs. Finally, the effect of SRL on CD8(+) Treg cells was evaluated. In vitro analysis of PBMCs isolated from KTRs showed that SRL suppressed Th17 cell differentiation but TAC did not. Conversion from TAC to SRL markedly decreased the number of effector memory CD8(+) T cells and significantly increased the proportion of CD4(+) and CD8(+) Treg cells compared with TAC in KTRs. SRL treatment induced the CD8(+) Treg cells, and these cells inhibited the proliferation of allogeneic CD4(+) T cells and Th17 cells. In conclusion, conversion from TAC to SRL favourably regulates Th17 and Treg cell differentiation in KTRs. These findings provide a rationale for conversion from TAC to SRL in KTRs.

Clinically-relevant cyclosporin and rapamycin concentrations enhance regulatory T cell function to a similar extent but with different mechanisms: an in-vitro study in healthy humans

Evidence indicates that regulatory T cells (Tregs) are profoundly involved in promoting allograft tolerance after organ transplantation. Since a successful transplantation currently still requires a long-term immunosuppressive treatment, clarifying the specific impact of these drugs on Tregs may be of high clinical relevance. Conflicting results arise from the literature, particularly as concerns cyclosporine (CsA). The specific aim of this work was to evaluate in-vitro the direct effects of clinically-relevant drug concentrations of three widely used immunosuppressive drugs, i.e. CsA, rapamycin (RAPA) and mycophenolic acid (MPA), on Treg activity, number and forkhead/winged helix transcription factor (FoxP3) expression in humans. Tregs (CD4(+)CD25(+)) isolated from healthy donors were cultured in the presence of different concentrations of CsA, RAPA or MPA. The suppressive activity of Tregs was evaluated in mixed lymphocyte reactions with CD4(+)CD25(-) T cells. Phenotype analysis and FoxP3 expression were assessed by flow cytometry. Clinically-relevant CsA and RAPA concentrations significantly enhanced to a similar extent the suppressive activity of Tregs. Although this effect was associated with an increase in Treg number as well as in FoxP3 expression with both drugs, the driving mechanism seemed to be primarily quantitative (i.e. increase of the cell number) for RAPA, whereas mainly qualitative (i.e. increase in FoxP3 levels) for CsA, respectively. Conversely, MPA did not show any effect on Treg function and number. These findings suggest that both RAPA and CsA may be beneficial in promoting Treg-dependent allograft tolerance after organ transplantation.

Decrease of immature B cell and interleukin-10 during early-post-transplant period in renal transplant recipients under tacrolimus based immunosuppression

B lymphocytes are known to play a role in kidney transplantation (KT) outcomes. Here, we evaluated the proportion of B cell subsets before and after KT. Twenty-one patients, who showed stable allograft function without acute rejection in the month following the KT, were included in this study. Peripheral blood samples were obtained from these patients before transplantation as well as 1month after transplantation. Changes in the proportion of B cell subsets after transplantation were investigated using multi-color flow cytometry. The proportion of lymphocytes in the peripheral blood mononuclear cells (PBMCs) and of CD19(+) B cells in the total leukocyte population did not change after KT. Similarly, the proportions of CD19(+)CD24(+) lymphocytes, mature B cells (CD24(Int)CD38(Inter)/CD19(+)), and memory B cells (CD24(+)CD38(-)/CD19(+)) did not change post-KT. However, the proportion of immature B cells (CD24(+)CD38(+)/CD19(+) B cells) decreased significantly after transplantation (P<0.01). The levels of IL-10, and IL-21, and expression of the B cell marker BLNK also decreased significantly after transplantation. Incubation of PBMCs with tacrolimus (0.1, 1, and 10ng/mL) and mycophenolate mofetil (200μg/mL) an immunosuppressant, resulted in significant reduction in the percentage of immature B cells. In contrast, the proportion of memory and mature B cells was not affected. Taken together, these results show that while the total B lymphocyte count and the proportion of memory/mature B cell subsets do not change after KT, the proportion of immature B cells and the associated cytokines that they secrete decrease significantly.

CD4+CD25+ regulatory T cells-derived exosomes prolonged kidney allograft survival in a rat model

CD4(+)CD25(+) regulatory T cells (Tregs) are negative regulators of the immune system that induce and maintain immune tolerance. Exosomes are natural products released from many sources and play a role in antigen presentation, immunoregulation, and signal transduction. In order to determine whether exosomes can be released from Tregs and participate in transplantation tolerance, we isolated and purified Tregs-derived exosomes and established a rat model of kidney transplantation. We then transferred the autologous exosomes into recipients to observe the effect of transplantation tolerance in vivo and in vitro. From in vivo study, serum analysis and histology showed that the function of exosomes can postpone allograft rejection and prolong the survival time of transplanted kidney. From in vitro study, exosomes possessed the capacity to suppress T cells proliferation. Taken together, these results suggest that the Tregs-derived exosomes have a suppressive role on acute rejection and inhibit T cells proliferation, especially exosomes derived from donor-type Tregs, which imply that the Tregs-derived exosomes are one of far-end regulation mechanisms of Tregs. Thus, exosomes released from Tregs could be considered as a possible immunosuppressive reagent for the treatment of transplant rejection.

Effects of immunosuppressive agents on Th17 cells involved in transplantation

The lymphocyte-derived helper T (Th) cells are critical regulators of the adaptive immune response and are associated with inflammatory disease. The most recently recognized Th-cell lineage, Th17, plays an important role in host defense against extracellular pathogens by secreting the proinflammatory cytokine, interleukin 17, and recruiting reactive oxygen species (ROS)-producing monocytes to the site of infection. However, accumulating evidence has implicated Th17-cell dysregulation as an underlying cause for some immune-related pathogenic conditions, including allograft rejection. Recent studies of human transplant patients have indicated that Th17 cells exhibit resistance to current immunosuppressive therapies that would otherwise prevent allograft rejection. In this review, we will discuss the most current research findings related to Th17-cell function in various kinds of allografts.

Dysregulation of Th17 cells during the early post-transplant period in patients under calcineurin inhibitor based immunosuppression

Accumulating evidence suggests that Th17 cells play a role in the development of chronic allograft injury in transplantation of various organs. However, the influence of current immunosuppressants on Th17-associated immune responses has not been fully investigated. We prospectively investigated the changes in Th17 cells in peripheral blood mononuclear cells (PBMCs) collected before and 1 and 3 months after KT in 26 patients and we investigated the suppressive effect of tacrolimus on Th17 in vitro. In the early posttransplant period, the percentage of Th17 cells and the proportion of IL-17-producing cells in the effector memory T cells (TEM) were significantly increased at 3 months after transplantation compared with before transplantation (P<0.05), whereas Th1/Th2 cells and TEM cells were significantly decreased. The degree of increase in Th17 during the early posttransplant period was significantly associated with allograft function at 1 year after transplantation (r = 0.4, P<0.05). In vitro, tacrolimus suppressed Th1 and Th2 cells in a concentration-dependent manner, but did not suppress Th17 cells even at high concentration. This suggests that current immunosuppression based on tacrolimus is inadequate to suppress Th17 cells in KTRs, and dysregulation of Th17 may be associated with the progression of CAD.

CD4(+)Foxp3(+) regulatory T cell therapy in transplantation

Regulatory T cells (Tregs) are long-lived cells that suppress immune responses in vivo in a dominant and antigen-specific manner. Therefore, therapeutic application of Tregs to control unwanted immune responses is an active area of investigation. Tregs can confer long-term protection against auto-inflammatory diseases in mouse models. They have also been shown to be effective in suppressing alloimmunity in models of graft-versus-host disease and organ transplantation. Building on extensive research in Treg biology and preclinical testing of therapeutic efficacy over the past decade, we are now at the point of evaluating the safety and efficacy of Treg therapy in humans. This review focuses on developing therapy for transplantation using CD4(+)Foxp3(+) Tregs, with an emphasis on the studies that have informed clinical approaches that aim to maximize the benefits while overcoming the challenges and risks of Treg cell therapy.

Tacrolimus trough levels and level-to-dose ratio in stable renal transplant patients converted to a once-daily regimen

Numerous evidence has been reported to support a safe 1:1 conversion from the twice-daily tacrolimus (Tac-T) to the once-daily tacrolimus regimen (Tac-O), but frequently there is a reduction in drug trough levels, which has been estimated by some authors to be about 20%. The relationship between Tac-O dosage and trough levels after conversion is not clear. The tacrolimus trough levels-to-dose ratio has been applied to better define the wide variability in doses and blood levels of tacrolimus. The aim of this study was to evaluate tacrolimus trough levels, tacrolimus daily dosage, and tacrolimus level-to-dose ratio during 1 year pre-postconversion follow-up in 31 stable kidney transplant patients who had received Tac-T therapy for over 6 months with stable renal function. They were converted to the same dosage of Tac-O. Patients before and after conversion were their own controls. The trough levels of tacrolimus showed a slight albeit significant reduction after conversion, remaining in the therapeutic range. Nineteen percent underwent an adjustment in total daily dosage after conversion versus 39% before conversion with no significant difference. No significant differences were detected in the total daily dose administered either by tacrolimus level-to-dose ratio before or after conversion. Kidney transplant recipients under Tac-O therapy were safely maintained using the same therapeutic monitoring as when receiving Tac-T.

CNI induced Th17/Treg imbalance and susceptibility to renal dysfunction in renal transplantation

Calcineurin inhibitors (CNI) prevent graft rejection by blocking interleukin-2 (IL-2), which was required for development and function of Foxp3(+)CD4(+)CD25(+) regulatory T cells (Treg). Recently, IL-2 was reported to play a part in the inhibition of Th17 cells. The renal transplantation recipient who used CNI regularly might have Th17/Treg imbalance with increased Th17 cells and decreased Treg cells, which would cause renal dysfunction even rejection. To assess the effect of CNI on Th17 cells and Treg cells, we included 123 renal transplantation recipients (101 in a stable stage and 22 with renal dysfunction) and 27 healthy volunteers. Among all the recipients, 103 recipients used CNI and 20 recipients used sirolimus without CNI. The recipients who used CNI were further classified into four groups according to the blood levels of CNI: Of all these subjects, Th17 and Treg frequencies in the peripheral blood were analyzed by flow cytometry (FCM). Serums IL-17, IL-23, IL-6, IFN-r, and TGF-β were analyzed by ELISA. The results demonstrated that the transplantation recipient treated by CNI revealed an obvious increase in peripheral Th17 frequencies and a significant decrease in Treg frequencies when compared with the sirolimus group and healthy people (P<0.05). Even more, the transplantation recipient with renal dysfunction had the highest level of Th17 cells (P<0.05) while the lowest Treg cells compared with stable recipient and healthy control, with increased serums IL-6 and IL-17. Our results indicated that CNI was associated with Th17/Treg imbalance in peripheral blood, which supported the followed generation of renal dysfunction after transplantation.

Bidirectional immunoregulation of calcineurin inhibitor tacrolimus on FOXP3 transcription?

The imbalance between regulatory T cells (Treg) and effector T cells is important for maintaining of psoriasis vulgaris. FOXP3 is a master control transcription factor for the development and function of Tregs and is critical for transcriptional repression. Tacrolimus is effective in treatment of psoriasis vulgaris. Data show that tacrolimus has multiple impacts on FOXP3, but the exact pharmacological mechanism of tacrolimus on FOXP3 have yet to be elucidated. We herein suggest the bidirectional immunoregulation of tacrolimus on FOXP3. High concentration of tacrolimus renders the cooperation of NFAT with STAT6 and NF-κB to activate GATA3 transcription. On the contrary, low concentration of tacrolimus results in higher nucleus level of NFAT, which directly binds to FOXP3 enhancer and/or cooperates with Smad3 to activate FOXP3 transcription. Further studies using loss of function and over-expression methods are needed to determine the detailed molecules involved in this bidirectional immunoregulation of tacrolimus on FOXP3.

Donor antigen-specific regulatory T-cell function affects outcome in kidney transplant recipients

Chronic transplant dysfunction, a major impediment to long-term allograft survival, is caused by several factors including an ongoing alloimmune response termed chronic rejection. To define some of these factors further, we selected 107 patients mismatched to their donors from 623 patients transplanted at a single center. Patients were categorized according to their immunosuppressive treatment and further divided into those with stable or chronic allograft dysfunction. Donor human lymphocyte antigen allopeptide-specific T-cell lines were then generated from stable patients and those with biopsy-proven chronic allograft nephropathy. Increased amounts of CD4+CD25+ regulatory T cells (Tregs) and Treg-associated gene expression profiles were found in cell lines derived from the patients with stable compared with those with chronic allograft dysfunction. Furthermore, a higher percentage of Tregs was found in patients with stable graft function on tacrolimus-based compared with cyclosporine-based immunosuppression protocols. Patients with stable graft function had a significantly higher expression of interleukin (IL)-4 and IL-10, whereas the cytokines IL-2, IL-17, and interferon-γ were significantly higher in patients with allograft dysfunction in vitro. Thus, enhancing the operational role of naturally occurring donor-specific Tregs in allograft recipients by adjusting the immunosuppression protocol may be advantageous particularly for patients with ongoing chronic rejection.

The effects of immunosuppressive drugs on CD4(+) CD25(+) regulatory T cells: a systematic review of clinical and basic research

OBJECTIVE

To review the effects of different immunosuppressive drugs on proliferation and function of regulatory T cells (Tregs).

METHODS

We searched MEDLINE, Embase (from inception to September 2009), and the Cochrane Library (Issue 4, 2009) for clinical and basic research about the effects of various immunosuppressive drugs on Tregs. Data were extracted and methodological quality was assessed by two independent reviewers. Outcome measures for clinical research included blood Tregs levels, acute rejection episodes, and graft function. Outcomes for basic research included percentage of Tregs proliferation, function, Tregs phenotype, and evidence for possible mechanisms. We analyzed data qualitatively.

RESULTS

Forty-two studies, including 19 clinical trials and 23 basic studies, were included. The immunosuppressive drugs studied were calcineurin inhibitors (CNIs), Rapa, anti-metabolism drugs, IL-2 receptor-blocking antibodies, T-cell depleting antibodies, and co-stimulation blockade antibodies. Most of the studies were on Rapa and CNIs. Eight basic studies on Rapa and CNIs showed that Rapa could promote the proliferation and function of Tregs, while CNIs could not. Five clinical trials involving a total of 158 patients showed that patients taking Rapa had higher blood concentration of Tregs than patients taking CNIs, but no difference was found in graft function (6-42 months follow-up).

CONCLUSION

There is substantial evidence that Rapa favors Tregs survival and function. However, the higher numbers of blood Tregs in patients treated with Rapa do not show any association with better graft function. Larger clinical studies with longer follow-up are needed to more thoroughly assess the efficacy of immunosuppressive drugs on Tregs, and reveal whether a relationship exists between Tregs and graft function.